Vertical wafer cleaning and drying system

ABSTRACT

A wafer cleaning and drying apparatus comprises a vertical wafer drive assembly providing two-sided wafer cleaning by symmetrically disposed brushes. Each wafer brush comprises two parallel rotatable shafts within the lumen of a substantially tubular sponge, with an adjustable distance between the two shafts, which is narrowed to facilitate insertion into the sponge and widened to stretch the sponge into a substantially oval cross-sectional shape, thereby improving traction. One or more nonrotating perforated fluid delivery tubes are mounted within the lumen of the sponge in the space between the two shafts. The apparatus further comprises a minimal volume rinse/dry enclosure that conserves water and process chemicals; and a wafer transport assembly configured to transfer multiple wafers simultaneously between multiple process stations.

This application is a division of application Ser. No. 08/972,775, filedNov. 18, 1997, now U.S. Pat. No. 5,933,302, issued on Aug. 10, 1999.

FIELD OF THE INVENTION

This invention relates to cleaning and drying of silicon semiconductorwafers. More particularly, this invention relates to apparatus forcleaning and drying a semiconductor wafer.

BACKGROUND OF THE INVENTION

Conventional semiconductor wafer cleaning apparatus suffers from avariety of general drawbacks. These include less than desired productionthroughput; excessive downtime for maintenance; inadequately cleanwafers due to inefficient surface scrubbing, contaminant removal, anddebris removal; excessive wafer breakage; lack of flexibility ofconfiguration and control to handle a variety of wafer sizes andgeometries; excessive consumption of processing fluids and otherconsumables; excessive generation of emissions and other industrialwastes; and excessive demand on manufacturing floor space.

Conventional wafer cleaning apparatus normally uses PVA (PolyvinylAlcohol) sponges as the cleaning elements. Conventional wafer cleaningmachines present several sponge related problems, including relativelyshort sponge service life due to particle buildup and excessive downtimeand handling requirements in conventional sponge replacement, leading tolong process requalification time. Moreover, conventional sponges arestretched onto a single shaft, which is normally oversized in order toavoid slippage between the sponge and the shaft under load.

The stretching of a sponge over a single oversized shaft in the priorart is a difficult operation and typically results in the surface of thesponge becoming lumpy and unevenly distributed on the shaft. Theresulting uneven sponge distribution often leads to non-uniform contactpressure between a rotating sponge and wafer, increasing the risk ofwafer breakage. Such nonuniformity and lumpiness impede the ability ofthe sponge to uniformly clean a wafer surface. Moreover the inability tohave a repeatable surface texture when sponges are replaced on the coredegrades the ability to predict the results of the cleaning process.Additionally, single-shaft mounted sponges on conventional machines aregenerally not efficiently rinsed, leading to contaminant buildup on thewafer and further contributing to shortened sponge life. Some cleaningequipment manufacturers rinse the sponge from the inside through asingle shaft, requiring rotary fluid feedthroughs.

Conventional wafer cleaning apparatus generally operates with the planeof the wafer oriented horizontally. This horizontal orientation occupiesmore floor space than is desirable and is typically difficult tomaintain, adversely affecting throughput. Horizontal wafer orientationfurther impedes efficient flushing away of contaminants and debris. GillU.S. Pat. No. 5,624,501 describes a wafer cleaning apparatus withvertically wafer orientation and two-sided brush cleaning, in which theopposed brushes are conically shaped. Kudo et al. U.S. Pat. No.5,547,515 describes a wafer cleaning method with vertically orientedwafers and simultaneous two-sided brush cleaning betweencounter-rotating tubular shaped brushes mounted on single shafts in abath. Jones et al. U.S. Pat. No. 5,486,134 describes a method fortexturing magnetic data storage disks, wherein the disk is orientedvertically between counter-rotating tubular shaped brushes mounted onsingle shafts and rotating in an upward direction along their respectivelines of contact with the disk. Thrasher et al. U.S. Pat. No. 5,475,889describes a brush assembly for cleaning horizontally oriented wafersbetween tubular shaped counter-rotating brushes, wherein the brushes aremounted respectively on single shafts. Holley et al. U.S. Pat. No.5,639,311 describes a method for cleaning horizontally oriented wafersbetween tubular shaped counter-rotating brushes, wherein the brushes aremounted respectively on single shafts and are irrigated internally withcleaning fluids. Akimoto U.S. Pat. No. 5,361,449 describes apparatus forcleaning horizontally oriented stationary wafers on the bottom surfaceonly, using a planetary mounted brush rotating in a plane parallel tothe wafer surface. Convac GmbH (Germany) previously used a horizontallyoriented non-interchangeable wafer mounting ring for double-sided wafercleaning.

Many conventional wafer cleaning systems support and rotate the wafer onits circumference using two or three grooved rolls. This drivearrangement is, however, subject to slippage, which may generatecontaminant particles and stresses that lead to wafer breakage. Theconventional wafer support and drive arrangement is also difficult toadapt to a variety of wafer sizes and shapes. Particularly, it isdifficult to support and rotate wafers having flats or notches on theiredges without generating mechanical shocks that increase the risk ofwafer breakage.

Conventional wafer drying apparatus frequently involves wafer spin/rinsecycles in which the wafers are mechanically moved, increasing the riskof breakage. In addition, high drying temperatures encountered in somewafer dryers may generate thermal stresses that further aggravate therisk of wafer breakage. Also, the spin/rinse cycles may damagephotoresist on patterned resist wafers. McConnell et al. U.S. Pat. No.4,911,761 and Mohindra et al. U.S. Pat. No. 5,571,337 describe processesfor drying without spinning, involving immersion in a rinse fluidfollowed by displacement of the rinse fluid by a drying vapor. Bran U.S.Pat. No. 5,539,995 describes a system for wafer drying without spinning,involving exposure of the wafer to a flowing vapor stream. Bran U.S.Pat. No. 5,556,479 describes a method and apparatus for wafer dryingwithout spinning, involving immersion in a rinse fluid that issubsequently displaced by a drying vapor, in which the wafer surface isheated radiantly. Several equipment manufacturers, for example VerteqInc. of Santa Ana, Calif. USA; YieldUP International of 117 Easy Street,Mountain View, Calif. USA 94043 (see for example bulletin D0013-6/96E),and Steag Microtech, of Germany offer a "MARANGONI" type rinse/drysystem in which the wafer remains motionless during the procedure and isdried using low-temperature dilute amounts of isopropyl alcohol in anitrogen carrier gas. Although this system reduces wafer breakage andchemical consumption, it typically involves relatively large processingchambers, and thus could benefit from further reduction in size toreduce chemical consumption and manufacturing floor space demands.

Conventional wafer cleaning transport assemblies are cumbersome, poorlyintegrated into process requirements and apparatus, subject tocontamination, and excessively demanding of manufacturing floor space.Some wafer transport assemblies require wafers to be transported singlyor collectively in cassettes or baskets. Thietje U.S. Pat. No. 5,468,302describes a wafer transport assembly, wherein vertically oriented wafersare individually moved between process stations using a pair ofindependent robotic devices sliding on a common rail. Lutz U.S. Pat. No.5,529,638 describes a wafer transport method, wherein wafers areindividually floated along a fluid track. Kudo et al. U.S. Pat. No.5,547,515 describes a method for wafer transport, wherein wafer edgesare gripped between elastically deformable arms that move linearly withrespect to each other to engage and release the wafer edges.

Accordingly the art needs a semiconductor cleaning and drying apparatushaving increased production throughput; lower downtime for maintenance;more efficient contamination control, surface scrubbing, and debrisremoval; reduced wafer breakage; greater flexibility of configurationand control to handle a larger variety of wafer sizes and geometries;lower consumption of processing fluids and other consumables; lowergeneration of emissions and other industrial wastes; and lower demand onmanufacturing floor space.

Particularly, the art needs a new sponge assembly configuration thatreduces handling, eliminates distortion of the sponge, promotesefficient rinsing and flushing of particles and other contaminants, andincreases service life between sponge replacements. Also needed is anapparatus to overcome the drawbacks in conventional horizontal wafersupport and rotation arrangements, including limited brush access,inefficient rinsing and flushing, drive slippage and particlegeneration, and limitations in sizes and shapes of wafers that can beaccommodated. Further needed is a rinse/dry apparatus that minimizesfloor space requirements and process chemical consumption, at the sametime keeping the wafer motionless and avoiding high temperatures.Additionally needed is a wafer transport apparatus occupying a minimalfootprint, capable of efficiently transferring multiple waferssimultaneously among multiple process sites.

SUMMARY OF THE INVENTION

In accordance with the present invention, a wafer cleaning and dryingapparatus comprises a wafer drive assembly that orients and supports awafer in a vertical plane, providing simultaneous access for wafercleaning brushes disposed symmetrically on both planar surfaces of thewafer. The symmetric configuration balances stresses on the wafersurfaces and reduces breakage. Each wafer brush comprises two parallelrotatable shafts, one of which is driven externally. Both shafts aremounted within the lumen of a substantially tubular sponge (or othersimilar soft, porous, and resilient material), with an adjustabledistance between the two shafts that is made narrower to facilitateinsertion of the shafts into the lumen of the sponge and is made wider,stretching the sponge into a substantially oval cross-sectional shape,to provide traction between the rotating shafts and the tubular sponge.One or more perforated fluid delivery tubes are also mounted within thelumen in a space between the shafts, but do not rotate with the shafts,thereby requiring no rotary fluid feedthroughs.

In operation, as the wafer rotates in a vertical plane, the spongesrotate in mutually opposite directions in a belt-like configurationabout their respective shafts, both parallel to the surfaces of thewafer, such that each sponge is traveling downward along the line ofcontact with the wafer. In this manner contaminants are carried downwardfrom the wafer surface into a drain. Concurrently fluid is dispensedfrom the fluid delivery tube to irrigate the sponge from the insidesurface just after the sponge passes over a rotating shaft. Thisirrigation can take place following contact of the sponge with either orboth of the rotating shafts, and can result in a beneficial cycle ofirrigation and squeezing, as the sponge is alternately compressed duringcontact with the shafts and expanded between the shafts.

At the end of a cleaning cycle the wafer cleaning brushes are eachmounted to swivel away from contact with the wafer surfaces about one oftheir respective rotation axes, thereby providing access to load andunload wafers in the wafer drive assembly.

In accordance with an embodiment, the wafer drive assembly rotates thewafer on six grooved rolls contacting the edge of the wafer. Each rollis mounted to a swivelable arm assembly, through which the rolls arecoupled to pulleys that are simultaneously driven by a single belt orother conventional means. The swivelable arms are linked in pairs, sothat both arms of a given pair are constrained to swivel symmetrically.This permits a linked pair of arms to swivel symmetrically away from thewafer drive assembly to allow access for loading and unloading wafers.It also prevents the wafer from jumping toward a roll that is beingpassed by a flat, since the linked pair configuration guarantees thatthe other five rolls remain in contact with the edge of the wafer.Additionally it provides for easy adjustment to accommodate differentwafer sizes.

In accordance with a further embodiment, the wafer drive assemblycomprises a rotating ring assembly clamping the edge of the wafer withslidable clamps mounted on a preloaded torsion spring lever swivelablymounted to an annular ring. The annular ring rotates on three rolls, oneof which is driven externally. When the annular ring is stationary in a"home" position, an actuator applies pressure laterally against contactpins mounted to the torsion spring levers, overcoming the preload springtension and causing the spring levers to swivel, withdrawing theslidable clamps from the edge of the wafer. This configuration allowsfor flexible interchange of ring assemblies tailored for specificdifferent wafer sizes and shapes. Additionally the single roll driveguarantees slip free rotation and consequently potentially reducedgeneration of contaminant particles.

In accordance with an embodiment, the apparatus comprises a compactrinse/dry module, in which the wafer is held stationary within a sealedenclosure, where it is immersed in a fluid, e.g. deionized water, andthen dried by exposure to a chemical vapor, e.g. isopropyl alcohol in anitrogen carrier gas. The enclosure is dimensioned with a minimal innervolume closely coupled about the wafer, thereby minimizing water andprocess chemical consumption. Rinsing and drying insingle-wafer-per-fill batches reduces the risk of cross contamination.

The enclosure divides into two portions, which separate to provideaccess for loading and unloading the wafer. The rinse/dry module furthercomprises one or more fluid dispensing nozzles adjacent and directedonto the wafer and the inner surface of the enclosure, maintainingmoisture, thoroughly rinsing, and flushing away contaminants prior tosealing the wafer inside the enclosure for drying. The fluid dispensingnozzles are turned off during and after drying of the wafer.

In accordance with an embodiment, the apparatus further comprises awafer transport assembly having a substantially cylindrical spacing barrotatably mounted in a transport housing translatable parallel to thespacing bar. At least two parallel lever assemblies are attachedradially to the spacing bar. Distal to the spacing bar each leverassembly is swivelably connected to two end effectors. Grooved cylindersattached to the end effector grip the edge of a wafer in a preciseposition and orientation, when the end effectors are swiveled closed,and release the wafer when the end effectors are swiveled open.

Fluid dispensing nozzles attached respectively to all but one of thelever assemblies spray and moisten the wafers continuously duringtransport.

In normal operation the transport housing starts at a home position withlever assemblies oriented vertically and the end effectors swiveledopen. The spacing bar rotates the lever assemblies into the horizontalplane. End effectors are then swiveled into the closed position, therebyenabling simultaneous capturing of wafers from multiple modules. Thespacing bar then rotates the lever assemblies into the vertical plane,removing the wafers. Then the housing translates the assembly by onemodule width, the lever arms are rotated into the horizontal plane, andthe end effectors are opened, placing the wafers in their respectivenext modules. After delivering the wafers, the lever assemblies arerotated again to the vertical plane, and the housing translates back tothe "home" position. This final translation may occur simultaneouslywith the ongoing processing of the wafers in the modules, therebyreducing wafer handling overhead and improving throughput.

At the beginning of a production cycle, only the first module contains awafer. During the first transport cycle, the wafer transport assemblycaptures and transfers the single wafer from the first module to thesecond module. During the second transport cycle, the wafer transportassembly captures and transfers the first wafer from the second moduleto the third module and simultaneously captures and transfers a secondwafer from the first module to the second module. At each successivetransport cycle the wafer transport assembly transfers one additionalwafer, until every module contains a wafer. At the end of a productioncycle the wafer transport assembly transfers one less wafer at eachsuccessive transport cycle, until only the last module contains a wafer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of a modular embodiment of a wafer cleaningand drying apparatus in accordance with the present invention.

FIG. 2 is a cutaway isometric view of a brush station module inaccordance with an embodiment of the present invention.

FIG. 3a is an isometric view of a brush assembly prior to insertion intoa sponge.

FIG. 3b is an isometric view of a sponge partially slipped around theshafts of a brush assembly.

FIG. 3c is an isometric view of a sponge mounted in operating positionaround a brush assembly.

FIG. 4a is an exploded isometric view of a brush assembly.

FIG. 4b is an isometric view of a first receive block.

FIG. 5 is a cross-sectional view illustrating wafer cleaning brushes inoperation to clean a wafer.

FIG. 6 is a cutaway isometric view showing portions of the brush swiveland wafer drive apparatus.

FIG. 7 is a cutaway isometric view of a brush station module showingwafer cleaning brushes swiveled into the retracted position away fromthe wafer surfaces.

FIG. 8 is a cutaway isometric view of a vertical wafer drive apparatus,in accordance with an embodiment of the invention.

FIG. 9a is a cutaway isometric view of an alternative clamp ringembodiment of a wafer drive apparatus, shown in the operatingconfiguration.

FIG. 9b is a cutaway isometric view of an alternative clamp ringembodiment of a wafer drive apparatus, shown in a loading and unloadingconfiguration.

FIG. 10a is a cutaway isometric view of a rinse/dry station module inaccordance with an embodiment of the invention, shown with onecontainment chamber shaded for clarity.

FIG. 10b is a cutaway isometric view of an IPA vapor source assembly inaccordance with an embodiment of the invention.

FIG. 10c is a cutaway isometric view of a rinse/dry station module inaccordance with an embodiment of the invention, shown with containmentchambers in the closed position.

FIG. 11a is a cutaway isometric view of a wafer transport apparatus, inaccordance with an embodiment of the invention.

FIG. 11b is a cutaway isometric view of the detailed structure of thelever assembly and spacing bar of FIG. 11a, in accordance with anembodiment of the invention.

FIG. 12 is a cross-sectional view of the wafer transport apparatus ofFIG. 11a at a typical process module, during one stage of the wafertransport cycle.

FIG. 13 is a cross-sectional view of the wafer transport apparatus ofFIGS. 11, 12 at a typical process module, during a different stage ofthe wafer transport cycle.

FIG. 14a is an isometric view of the wafer transport apparatus of FIG.11a in one end position at the beginning of a transport cycle (homeposition), in accordance with the present embodiment.

FIGS. 14b-14h are isometric views of the wafer transport apparatus ofFIG. 11a at further stages of the transport cycle, in accordance withthe present embodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIG. 1 is an isometric view of a modular embodiment of a wafer cleaningand drying apparatus 100 in accordance with the present invention.Illustratively wafer cleaning and during apparatus 100 comprises a firstbrush station module 102, a second brush station module 104, a rinse/drystation module 106, and a wafer transport apparatus 108. Modules 102,104, 106, and apparatus 108 may be packaged as illustrated in FIG. 1 orin any other desired manner, including as individual modules. Wafercleaning and draining apparatus 100 may comprise more or fewer than onemodule of each type, and may additionally comprise modules of othertypes (not shown). Modules of the same type, e.g., brush station modules102, 104, may be identical to one another or may differ in structuraldetails, in function, or in process materials and variables such asfluids, sponges, pressures, and rotation speeds.

Illustratively, although two brush station modules 102, 104, may beadvantageous to perform a prewash and a separate final wash for improvedwafer cleanliness and manufacturing throughput (e.g. to keep pace withother manufacturing processes such as wafer polishing), wafer cleaningand draining apparatus 100 may alternatively incorporate only one brushstation module.

FIG. 2 is an isometric view of brush station module 102, 104 inaccordance with an embodiment of the present invention. A wafer 160 issupported and rotated in a vertical plane by a wafer drive apparatus170. Two wafer cleaning brushes 203a and 203b perform a contactscrubbing action simultaneously on parallel wafer surfaces 160a and 160b(not shown), respectively, of wafer 160.

FIGS. 3a-3c are isometric views of wafer cleaning brushes 203a, 203bduring progressive stages of assembly. Each wafer cleaning brush 203a,203b comprises two rotatable shafts (also referred to as cores), namelya master shaft 221 and a slave shaft 223, which are mounted parallel toeach other in a brush assembly 242 further comprising end blocks 244a,244b and 246a, 246b. Master shaft 221 is driven by a rotary drivemechanism (not shown) coupled to an end of master shaft 221.

Brush assembly 242 is inserted into a substantially tubular sponge orother similar soft, porous, and resilient material (hereinafter sponge107a, 107b) as shown in FIGS. 3a-3c. FIG. 3a is an isometric view ofbrush assembly 242 prior to insertion into sponge 107a, 107b. FIG. 3b isan isometric view of sponge 107a, 107b partially slipped around shafts221, 223. FIG. 3c is an isometric view of sponge 107a, 107b mounted inoperating position around brush assembly 242, such that the axis ofsponge 107a, 107b is aligned parallel to the axes of shafts 221, 223 anddoes not overlap end blocks 244a, 244b, 246a, 246b.

Sponge 107a, 107b is typically formed of PVA (polyvinyl alcohol) and issupplied in a sealed bag after being pre-moistened e.g., with deionizedwater. During use sponge 107a, 107b is always kept moistened, typicallybut not necessarily with deionized water, to insure that sponge 107a,107b has the proper surface moisture for cleaning wafers. Sponge 107a,107b has a length L (see FIG. 3a) typically slightly over 8 inches for8-inch diameter wafers and slightly over 12 inches for 12 inch diameterwafers. Length L may be specified in accordance with wafer diameters andshaft lengths.

In a preferred embodiment, sponges 107a, 107b consisting of PVA(polyvinyl alcohol) pre-moistened with deionized water are obtainable insealed packages from Rippey Corporation in Dorado Hills, Calif., or fromMerecel® Scientific Products, 950 Flanders Road, Mystic Conn. 06355.These sponges are designed particularly to be installed in a wafercleaning brush 203a, 203b of the type shown in FIGS. 3a-3c.

FIG. 4a is an exploded isometric view of brush assembly 242. Tofacilitate the installation of sponge 107a, 107b onto shafts 221, 223(see FIGS. 3a-3c), the distance between parallel shafts 221, 223 is madelaterally adjustable by means of adjustment screws 248 and dowel pins250. Adjustment screws 248 engage internal threads (not shown) in anupper end block 244a, 246a and bear against a lower end block 244b,246b. Turning adjustment screws 248 in one direction with a conventionaltool relieves the bearing force and allows shafts 221 and 223 to movelaterally toward each other, allowing sponge 107a, 107b to be slippedeasily onto brush assembly 242 without stretching (see FIG. 3b). Whenadjustment screws 248 are turned in an opposite direction, the bearingforce is increased, expanding the distance between shafts 221 and 223,which move laterally outward relative to each other. This outward motionis limited by contact with the lumen of sponge 107a, 107b, which exertsan elastic constraining force opposing the bearing force. End blocks244a, 246a are slidably guided by dowel pins 250, disposed one in eachend block 244b, 246b, to assure that the axes of shafts 221 and 223remain parallel with each other.

In an expanded condition, shafts 221 and 223 stretch sponge 107a, 107binto a substantially oval cross-sectional shape (see FIG. 3c).Sufficient traction is created between the contacting surfaces of sponge107a, 107b and shaft 221, 223, causing sponge 107a, 107b to followmaster shaft 221 and to drive slave shaft 223 rotationally withoutslippage.

Referring to FIG. 4a, rinse tubes 119a, 119b are installed in brushassemblies 242 along the length of shafts 221, 223, so that they lie ina space between shafts 221, 223 within the lumen of installed sponges107a, 107b, respectively. Rinse tubes 119a, 119b are attached rigidly toend blocks 244b, 246b, and thus do not rotate with shafts 221, 223;therefore rotary fluid feedthroughs are not required. Rinse tubes 119a,119b have fluid dispensing perforations 154 along their lengths.Perforations 154 are oriented to direct a spray outward from andsubstantially perpendicular to a midplane 156 containing axes of bothshafts 221, 223 of brush assembly 242, and are slit-shaped with theirmajor axes parallel to the axes of shafts 221, 223.

Also installed in brush assemblies 242 inserted within sponges 107a,107b along the length of shafts 221, 223 are delivery tubes 120a, 120b.Delivery tubes 120a, 120b are attached rigidly to end blocks 244b, 246b,and thus do not rotate with shafts 221, 223; therefore rotary fluidfeedthroughs are not required. Delivery tubes 120a, 120b have fluiddispensing perforations (not shown) along their lengths, similar torinse tubes 119a, 119b. In the present embodiment the perforations offluid delivery tubes 120a, 120b are directed outward and in a directionopposite from perforations 154 of rinse tubes 119a, 119b, and arelikewise slit-shaped with their major axes parallel to the axes ofshafts 221, 223.

Delivery tubes 120a, 120b and rinse tubes 119a, 119b may besubstantially identical in structure, and may dispense either the samefluids or different fluids. Delivery tubes 120a, 120b and rinse tubes119a, 119b are designed in accordance with conventional hydrodynamicprinciples, so that they maintain substantially uniform pressurethroughout their respective lengths at their respective operating flowrates, and thus produce a longitudinally uniform spray pattern.

Delivery tubes 120a, 120b and rinse tubes 119a, 119b are connected at afirst end to first end block 244b, which contains fluid feedthroughs(not shown) to connect rinse tubes 119a, 119b and delivery tubes 120a,120b with pressurized fluid sources. Delivery tubes 120a, 120b and rinsetubes 119a, 119b are attached at a second end to second end block 246b,which may optionally contain fluid feedthroughs. End blocks 244a, 244b,246a, 246b also contain bearings (not shown) for rotation of shafts 221,223. Additionally, end blocks 244b, 246b each have a step 252 andoptional mounting holes 254 to facilitate installing wafer cleaningbrush 203a, 203b within brush station module 102, 104 (see FIG. 2) usingappropriate fasteners (not shown). An alternative to mounting holes 254is a compression collar 256, which straddles and clamps end blocks 244b,246b within brush station module 102, 104.

To install wafer cleaning brush 203a, 203b within brush station module102, 104 (see FIG. 2), first end block 244b is attached to a firstreceive block 112a, 112b located within brush station module 102, 104.FIG. 4b is an isometric view of first receive block 112a, 112b. Firstreceive block 112a, 112b has fluid feedthroughs that connect with thefluid feedthroughs of first end block 244b via fluid coupling seals(e.g., compression o-rings 258) to deliver fluids to first end block244b. Step 252 of first end block 244b (see FIG. 4a) positions first endblock 244b longitudinally onto first receive block 112a, 112b, to alignthe openings of fluid feedthroughs in first end block 244b with thecorresponding openings of fluid feedthroughs in first receive block112a, 112b (not shown). Referring to FIG. 2, second end block 246b issimilarly attached to a second receive block 114a, 114b located withinbrush station module 102, 104. In the present embodiment, fluidfeedthroughs and coupling seals are not required in second end block246b or second receive block 114a, 114b. End blocks 244b, 246b arefastened to receive blocks 12a, 112b, 114a, 14b using conventionalmeans, e.g., mounting holes 254 or compression collar 256 withappropriate conventional fasteners.

Receive blocks 112a, 114a and 112b, 114b respectively are mounted oncoaxial bearings 116 (see FIGS. 2, 4b) located in the process chamberwalls of brush station module 102, 104. Labyrinth sealing of coaxialbearings 116 prevents fluids inside the process chamber from leaking tothe outside of the process chamber. When installed into brush stationmodule 102, 104, receive blocks 112a, 114a swivel around an axis 280a,with which master shaft 221 is aligned. The swivel motion brings sponge107a into contact with wafer surface 160a for cleaning and retractssponge 107a away from wafer surface 160a to provide sufficient access toload and unload wafer 160 between cleaning cycles. Similarly receiveblocks 112b, 114b (not shown) swivel around an axis 280b, with whichmaster shaft 221 is aligned. The swivel motion brings sponge 107b intocontact with wafer surface 160b (not shown) for cleaning and retractssponge 107b away from wafer surface 160b to provide sufficient access toload and unload wafer 160 between cleaning cycles.

Second receive blocks 114a, 114b each contain an additional shaft (notshown), concentric with swivel axes 280a, 280b, which transmits arotational drive to master shafts 221. The connection between drivenmaster shaft 221 and the external driving shaft is preferably made usinga conventional tongue-and-groove mechanical coupling (not shown). Thiscoupling method advantageously prevents backlash, minimizes corrosionand particle generation, and permits wafer cleaning brushes 203a, 203bto be installed and removed by sliding in one direction withoutdisassembly of drive coupling or wafer cleaning brush, once the mountingfasteners are removed.

FIG. 5 is a cross-sectional view illustrating wafer cleaning brushes203a, 203b in operation to clean wafer 160. During the cleaning cycle,wafer cleaning brushes 203a, 203b cause sponges 107a, 107b to rotate,thereby causing the surfaces of sponges 107a, 107b to rub against andremove contaminants from surfaces 160a, 160b of wafer 160. The line ofcontact between sponges 107a, 107b and wafer surfaces 160a, 160b,respectively, lies on the major horizontal diameter of wafer 160 toprovide maximum cleaning coverage of wafer surfaces 160a, 160b. Wafer160 is simultaneously oriented and rotated in a vertical plane by waferdrive apparatus 170 (see FIG. 2), thereby ensuring that all points onwafer surfaces 160a, 160b are subjected during the rotation cycle ofwafer 160 to the scrubbing action of sponges 107a and 107b. Because ofwafer rotation, the contact areas of sponges 107a, 107b may dwell for alonger time on some portions more than other portions of the surfaces ofwafer 160. However, the cleaning cycle duration lasts long enough, sothat any disparity in contact or dwell time does not adversely affectthe overall cleanliness of the wafer.

The upper portions of wafer cleaning brushes 203a, 203b presssymmetrically against wafer surfaces 160a, 160b respectively. Ofimportance, the symmetry of stress against the plane of wafer 160reduces the risk of wafer breakage. Sponges 107a, 107b counterrotate,for example sponge 107b of wafer cleaning brush 203b rotates clockwise,whereas sponge 107a of wafer cleaning brush 203a rotatescounter-clockwise, as shown by arrows 111a and 111b, respectively. Thesenses of rotation illustrated in FIG. 5 are preferred to carrycontaminants efficiently away from wafer surfaces 160a, 160b on thesurfaces of sponges 107a and 107b and to discharge them downward into abottom drain 152 of brush station module 102, 104 (see FIG. 2).

Rinse tubes 119a, 119b are interconnected through first receive block112a, 112b with flexible supply tubes 109a, 109d respectively (see FIG.2), which supply deionized water or other cleaning fluid to rinse tubes119a, 119b. For example, deionized water may be supplied throughflexible tube 109a and then directed through fluid feedthroughs inreceive block 112a into rinse tube 119a, contained in wafer cleaningbrush 203a (see FIG. 5). Rinse tube 119a has perforated side walls toallow fluid within rinse tube 119a to be ejected laterally and tocontact and thus flush debris from sponge 107a. Likewise deionized watermay enter flexible tube 109d and in turn be delivered through receiveblock 112b to rinse tube 119b contained in wafer cleaning brush 203b.Deionized water then is ejected laterally from rinse tube 119b throughperforations along its length to contact and flush debris from sponge107b.

Delivery tubes 120a and 120b are interconnected through first receiveblock 112a, 112b with flexible supply tubes 109b, 109c respectivelywhich supply an additional fluid to be sprayed onto the inner surfacesof sponges 107a, 107b. For example, delivery tubes 120a, 120b, whichalso have slit-shaped perforations along their length, dispense cleaningfluids or any other chemicals or appropriate fluids for use in thecleaning of wafers 160 against and into sponges 107a and 107b. Thecounterclockwise rotation of sponge 107a of wafer cleaning brush 203aand the clockwise rotation of sponge 107b of wafer cleaning brush 203bcarry fluid ejected from delivery tubes 120a and 120b, respectively,into sponges 107a and 107b, which in turn directly contact wafersurfaces 160a and 160b, respectively where the ejected fluidsefficiently facilitate the process of cleaning wafer 160. Fluidsdelivered through delivery tubes 120a, 120b may include ammonia,ammonium hydroxide, dilute hydrofluoric acid (DHF), and any otherappropriate cleaning solution or fluid.

Rinse tubes 119a, 119b dispense deionized water or other cleaner fluidonto the lower inside surfaces of sponges 107a, 107b. Between shafts 221and 223, sponge 107a, 107b is in an expanded condition, thereby readilyabsorbent to fluid. In a typical configuration, a fluid from rinse tubes119a, 119b (normally deionized water) flushes sponges 107a, 107b fromthe inside directly after they have contacted wafer surfaces 160a, 160b.This portion of sponges 107a, 107b is removed from wafer surfaces 160a,160b, such that contaminant particles fall downward into thedrain/exhaust area of the process chamber. As sponge 107a, 107b isrolled around master shaft 221, sponge 107a, 107b is progressivelypressed radially by master shaft 221 to a more compressed condition,thereby squeezing out more contaminant carrying fluid. After passingaround master shaft 221, sponges 107a, 107b reexpand, and a second fluidfrom delivery tubes 120a, 120b (e.g. dilute ammonia or a surfactant)premoistens sponges 107a, 107b directly prior to contact with wafersurfaces 160a, 160b. The repeated cycle of sponge expansion andcompression facilitates flushing of contaminants from the surface ofsponge 107a, 107b, and discharging of waste fluid and contaminantsdownward into bottom drain 152 (see FIG. 2).

The operation of rinse tubes 119a, 119b and delivery tubes 120a, 120ballows independent control of deionized water and cleaning fluids or ofany two types of fluids. For example flow through rinse tubes 119a, 119bcan be shut off, while fluids are delivered only through delivery tubes120a, 120b if desired. Alternatively, the relative proportions of fluidsthrough tubes 119a, 119b and 120a, 120b, respectively, can be varied.

One or more external fluid nozzles, for example nozzle assembly 272, areprovided in each brush station module 102, 104. Nozzle assembly 272 maybe programmed to dispense fluids, for example chemicals and DI waterdirectly onto wafer surfaces 160a, 160b before, during, and after acleaning operation.

FIG. 6 is a cutaway isometric view showing portions of brush swivelapparatus. A low friction double acting air cylinder 260 may beinterconnected to first receive blocks 112a, 112b through a brushlinking plate 262 and swivel assemblies 264, to swivel wafer cleaningbrushes 203a, 203b about the respective axes of master shafts 221. Sinceair cylinder 260 maintains a constant pressure independent of its rodextension, it can assure uniform contact pressure between sponge 107a,107b and wafer surfaces 160a, 160b. Using a conventional belt-and-pulleyor chain-and-sprocket drive arrangement. swivel assemblies 264 aresymmetrically connected to brush linking plate 262. such that rotarymotion is converted to linear motion. Brush linking plate 262 slidesalong vertical rails 266 and is attached to the piston rod of aircylinder 260. This type of linking configuration is described in greaterdetail in the discussion of wafer drive assembly 170 below. Thesymmetric linkage divides contact pressure evenly between wafer cleaningbrushes 203a, 203b, and automatically compensates for wafer-to-waferthickness variations. In addition it assures that both wafer surfaces160a, 160b are contacted simultaneously and released simultaneously,reducing risk of breakage.

In operation, during the loading of wafer 160 into wafer drive apparatus170, wafer cleaning brushes are in the retracted orientation swiveledaway to provide clearance to load wafer 160 into wafer drive apparatus170. The piston rod of double acting air cylinder 260 is also retracted.At the beginning of a cleaning cycle the piston rod of double acting aircylinder 260 is extended, and the motion is coupled through brushlinking plate 262 and swivel assemblies 264 to press wafer cleaningbrushes 203a, 203b against wafer surfaces 160a. 160b (see FIG. 2).During a cleaning cycle double acting air cylinder 260 maintainspressure to hold wafer cleaning brushes 203a, 203b against wafersurfaces 160a, 160b. At the conclusion of a cleaning cycle the pistonrod of air cylinder 260 (see FIG. 6) is retracted, forcing brush linkingplate 262 to slide downward on vertical rails 266 and causing swivelassemblies 264 to swivel wafer cleaning brushes 203a, 203b away fromwafer surfaces 160a, 160b (see FIG. 7 and direction arrows 230a, 230b ofFIG. 5) into the retracted position. thereby providing sufficientclearance between wafer cleaning brushes 203a and 203b for wafertransport apparatus 108 (not shown, to be described in detail below) toremove wafer 160 from wafer drive apparatus 170 and to place anotherwafer into wafer drive apparatus 170. FIG. 7 is a cutaway isometric viewof brush station module 102, 104 showing wafer cleaning brushes 203a,203b swiveled into the retracted position away from wafer surfaces 160a,160b.

The use of two adjustable parallel shafts 221 and 223 in brush assembly242 is a feature that allows sponges 107a, 107b, in accordance with theembodiment, to be more uniform in surface texture during the cleaningoperation and overcomes the prior difficulties associated with mountinga sponge over a single core or shaft. With shafts 221, 223 in theclosest position to each other, brush assemblies 242 fit into the spongelumen with little or no contact or friction, enabling a stress freesponge installation. It is possible to leave the sponge in its originalpackaging material (typically a plastic bag) during sponge installation,provided one end of the bag is open, reducing handling and particlecontamination. The elimination of compressed and stretched areas in thelongitudinal direction results in an even longitudinal distribution ofsponge material along the shafts and thus improves the contact pressureuniformity between sponges 107a, 107b and wafer surfaces 160a, 160b.Uniform contact pressure in turn reduces stress on the wafer and therisk of wafer breakage. The adjustability of the distance between thetwo shafts allows controlling tension to achieve slippage-free spongerotation.

During operation, the repeated sequence of compression and expansion ofthe sponge material around the perimeter reduces particle penetrationinto the soft sponge material. Incorporation of fluid delivery tubeswithin the lumen of hollow sponges 107a, 107b in the space betweenshafts 221, 223 facilitates flushing of contaminants and debris fromwafer surfaces 160a, 160b and sponges 107a, 107b. Also rinsing andpre-wetting efficiency of the sponge material from internal fluiddelivery tubes improves flushing and discharging of contaminants awayfrom the wafer surfaces. With rinse tubes located within the lumen ofthe sponge, the flushing direction facilitates the desired particleflow. Continuous reconditioning (rinse) of sponges 107a, 107b leads toprocess consistency (each wafer processed under the same conditions),and extended sponge life between replacements. The embodiment requiresno rotary fluid feedthroughs, therefore, mechanical simplicity and fluidcleanliness is maintained.

Brush assemblies 242 may be equipped or coupled with sensors (not shown)to measure in situ processing parameters, such as brush contactpressure.

Typical rotation speed of wafer cleaning sponges 107a, 107b lies in arange of from 200 RPM to 400 RPM. A safe maximum wafer rotation speedwith tolerable breakage is roughly 200 RPM when wafer 160 is an 8 inchwafer. Under these conditions, a typical time to clean one wafer such aswafer 160 using the cleaning structure of this embodiment isapproximately one minute including insertion and removal of the wafer.The manner in which the wafer is inserted into and removed from waferdrive apparatus 170 is described in greater detail below.

Horizontal wafer drive configurations are a very common, and in someprocess steps probably a preferred orientation (CVD, resist coat,develop, etch, polish, etc.). In cleaning applications, both horizontaland vertical wafer orientation are common. Single wafer processingequipment in most cases involves a horizontal wafer. In batch processingwafers are traditionally mounted vertically. A vertically oriented waferoccupies a significantly smaller footprint and is less vulnerable torecontamination, because its critical surfaces are parallel to thedirection of gravity.

FIG. 8 is a cutaway isometric view of vertical wafer drive apparatus170, in accordance with an embodiment of the invention. The purpose ofwafer drive apparatus 170 is to rotate wafer 160 about its axis, withwafer surfaces 160a, 160b oriented vertically. A number of rolls172a-172f are arranged coplanar and in contact with the circumference ofwafer 160. A V-groove 174 around the circumference of each roll ensuresradial and axial positioning of wafer 160, while it is rotated about itsaxis. Rolls 172a-172f are individually mounted on roll arm assemblies176a-176f. During a cleaning operation, wafer 160 (see FIG. 2) must berotated about a fixed axis to maintain contact alignment of wafercleaning sponges 107a, 107b along the major horizontal diameter of wafer160 and to avoid mechanical shock or damage to wafer 160 due toimbalance. Three rolls would theoretically be sufficient to capture andcenter wafer 160.

However, wafers commonly in production have notches or flats 162 attheir circumferences (although notches or flats are not anticipated onthe newer 300 mm diameter wafer size). In a three-roll configuration,when a flat 162 passes adjacent a roll 172a-172c, wafer 160 tends tolurch toward that roll, thereby displacing the rotation axis andinducing mechanical shock to wafer 160. This may be prevented byincreasing the number of rolls above the theoretical minimum of three toassure centering of wafer 160 independent of the momentary position of anotch or flat 162. A wafer 160 with one flat 162, for example mightrequire a minimum of four rolls 172a-172d to maintain at least threerolls in contact with wafer 160 at all times. Further, the distancebetween any two consecutive rolls must be greater than the length of anotch or flat 162, so that a notch or flat 162 passes only one roll172a-172d at a given time. Additionally, a theoretical line connectingthe two rolls adjacent any roll 172a-172d which is temporarilydisengaged from wafer 160 at a passing notch or flat 162 must liebetween the center of wafer 160 and disengaged roll 172a-172d, in orderto keep the wafer centered. Therefore any two non-consecutiverolls-separated by a single roll 172a-172d must be spaced more closelytogether than a wafer diameter. This is impossible to achieve for acomplete set of four rolls simultaneously. Accordingly, to keep wafer160 centered, more than four rolls are needed, provided wafer 160 has anotch or a flat.

In accordance with the present embodiment, to prevent rolls 172a-172ffrom following the contour of flat 162, rolls 172a-172f are linkedtogether in pairs. A linked pair of rolls may follow wafer diametervariations only cooperatively but not individually. When flat 162 passesonly one roll 172a-172f at any given time, a linked roll maintains theradial position of the pair. Such a configuration will then ensure thatwafer 160 does not lurch in the direction of a roll 172a-172f adjacent aflat 162.

This configuration requires a minimum of six rolls 172a-172f for wafershaving a notch or flat 162, since above described considerations dictatethat there must be more than four rolls, and pairing dictates an evennumber of rolls. Further, in such a configuration at least one pair ofrolls must be retractable for loading or unloading wafer 160 from thetop or side. Two fixed rolls 172a, 172b are mounted on a pair ofstationary arm assemblies 176a, 176b, and fix the rotation axis of wafer160. Fixed rolls 172a, 172b are disposed symmetrically with respect tothe vertical axis of wafer 160 and below the rotation axis of wafer 160,so that they do not interfere with wafer cleaning brushes 203a, 203b(see FIG. 7) or with the loading and unloading of wafer 160. Stationaryarm assemblies 176a, 176b are adjustable to accommodate varying waferdiameters.

Two linked upper rolls 172c, 172d, mounted to upper swivelable armassemblies 176c, 176d, preload wafer 160 against fixed rolls 172a, 172b.Two linked lower rolls 172e, 172f, mounted to lower swivelable armassemblies 176e, 176f, stabilize the rotation axis of wafer 160 againsttemporary disengagement of fixed rolls 172a, 172b due to passing flatsand notches 162. Linked upper rolls 172c, 172d and linked lower rolls172e, 172f engage the circumference of wafer 160 under spring loading,which enables them to adapt automatically to variations in waferdiameter.

Within each arm assembly 176a-176f is a drive mechanism (not shown)consisting of pulleys and a belt transmitting the rotation of a shaftassembly, concentric with each swivel axis, to its respective roll.Concentric shaft assemblies 178a-178f and swivel mechanisms extendthrough bearings mounted on a structural wall 168 of brush stationmodule 102, 104 (see FIG. 6). All six shaft assemblies are driven by asingle drive belt 180 connected to a motor (not shown). Using a singlebelt results in closely synchronized roll speeds, minimizing slippagebetween rolls and wafer. The amount of slippage is determined by contactpressure plus radial tolerances among the component rolls, shafts, andpulleys. The contact pressure between roll and wafer should be at leastadequate for slip free motion but substantially below the wafer breakagelevel.

The swivel drive and radial stabilization of arm assemblies 176c-176fare achieved by converting rotary to linear motion using belts andpulleys (sprockets and chains are alternatives). The routing of thebelts around the pulleys is such that one arm of each coupled pairswivels in clockwise direction and the other arm swivelscounterclockwise, ensuring a symmetric arm configuration relative to thevertical axis of wafer 160.

As shown in FIG. 6, lower swivelable arms 176e, 176f are connectedrigidly along their respective swivel axes through structural wall 168to lower swivel pulleys 182e, 182f. Each lower swivel pulley 182e, 182fdrives a lower swivel belt 184e, 184f respectively. Both ends of eachlower swivel belt 184e, 184f are attached to a lower linking plate 186.Lower linking plate 186 in turn slides along vertical rails 188. Anadjustable lower compression spring 190 supports the weight of lowerlinking plate 186. Lower compression spring 190 also provides thedesired amount of preload (contact pressure) to linked lower rolls 172e,172f. Lower compression spring 190 is adjusted for a particular wafersize by balancing the weight of lower linking plate 186 at anequilibrium position in which linked lower rolls 172e, 172f are locatedslightly closer to the center of wafer 160 than the actual wafer radius.

After wafer 160 is loaded, its weight and the preload of linked upperrolls 172c, 1772d compensate for this positional offset. With a loadedwafer 160, linked lower rolls 172e, 172f contact the wafer edge with apressure proportional to the setting of compression spring 190. If aflat or a notch 162 passes one of two linked lower rolls 172e, 172f, itsposition remains the same because the paired linked roll 172e, 172fretains contact with the wafer edge, thus maintaining the verticalposition of lower linking plate 186 unchanged. The contact pressurebetween the engaged linked lower roll 172e, 172f and the wafer will beapproximately doubled. Therefore the amount of set preload should neverexceed half of the maximum permitted value.

The linkage of the two upper arm assemblies 176c, 176d is similar tothat described above for linked lower arm assemblies 176e, 176f. Upperarm assemblies 176c, 176d need to swivel between two predeterminedpositions for a given wafer size. In the open position (arms vertical) awafer can be loaded or unloaded. After a wafer is loaded, the armsclose. Upper arm assemblies 176c, 176d are connected through structuralwall 168 to upper swivel pulleys 182c, 182d, respectively. Each upperswivel pulley 182c, 182d is coupled through an upper swivel belt 184c,184d, respectively, to an upper linking plate 192. Both ends of eachupper swivel belt 184c, 184d are attached to upper linking plate 192.The routing of belts 184c, 184d around pulleys 182c, 182d is similar tothat describing lower linking plate 186 above. Upper linking plate 192slides along vertical rails 188 (optionally sharing the same rails withlower linking plate 186). A subplate 194 is captively coupled within arecess of upper linking plate 192 and is rigidly connected to the pistonrod of a low friction double acting air cylinder 196.

When the piston rod of air cylinder 196 is extended, it forces attachedsubplate 194 upward against an upper compression spring 198, which inturn pushes upward against the recess of upper linking plate 192,causing attached upper swivel belts 184c, 184d to actuate upper swivelpulleys 182c, 182d and thereby causing upper arm assemblies 176c, 176dto close. Shortly before subplate 194 reaches its upper end position,upper rolls 172c, 172d touch the edge of wafer 160. Upper compressionspring 198, which is adjustable by means of adjustment screw 199, isused to adjust the contact pressure of upper rolls 172c, 172d, againstthe circumference of wafer 160. When upper rolls 172c, 172d touch thewafer edge, upper link plate 192 stops traveling upward. The positionaloverrun of subplate 194 is converted into an adjustable preload. Aftersubplate 194 reaches equilibrium with its load, piston rod of aircylinder 196 (rigidly attached to subplate 194) stops in an extendedposition. The degree of arm swivel to accept a different wafer size canbe changed using a relocatable end stop 200, which limits the range oftravel of upper linking plate 192. By driving two arm assemblies 176c,176d with a common air cylinder 196 by way of upper linking plate 192,the two arm assemblies are caused to close symmetrically, minimizing therisk of mechanical shock or displacement of the wafer.

In case of a passing notch or flat 162 the same linking operation willoccur as described above for lower arm assemblies 176e, 176f. When thepiston rod of air cylinder 196 is retracted, subplate 194 moves downwardfirst, releasing the preload. When the bottom surface of captivesubplate 194 engages and pulls downward on upper link plate 192, upperarms 176c, 176d begin to swivel open.

To adapt to a different wafer size, lower arm assemblies 176e, 176f arerepositioned without changing the preload. Upper arm assemblies 176c,176d adapt to a new wafer size automatically, since the contact pressureis independent of rod extension.

In accordance with the embodiment, vertical wafer drive apparatus 170allows easy brush access to both critical wafer surfaces 160a, 160bsimultaneously. Different wafer sizes are readily accommodated byadjusting the positions of arm assemblies 176a-176f. Wafer driveapparatus 170 can smoothly rotate wafers with one notch or flat, withoutlateral displacement of the wafer rotation axis or potentially damagingmechanical shocks. Simultaneous drive of all rolls 172a-172f minimizesslippage, reducing mechanical stress and particle generation.

FIGS. 9a and 9b are cutaway isometric views of an alternative embodimentof wafer drive apparatus 126, in accordance with the invention.Referring to FIG. 9a, wafer drive apparatus 126 comprises a ringassembly 128, into which wafer 160 is rigidly clamped and rotated in avertical plane. Ring assembly 128 comprises an annular ring 130 to whichare attached two torsion spring preloaded levers 136a, 136b, havingslotted clamps 140a, 140b, respectively, and contact pins 146a, 146b,respectively. Two fixed slotted clamps 138a, 138b are attached directlyto annular rim 130. In one embodiment torsion spring preloaded levers136a, 136b are pivotally attached to annular ring 130 on PTFE bushings(not shown) with shoulder screws 147a, 147b. Connected between torsionspring preloaded levers 136a, 136b respectively and annular ring 130 andencircling shoulder screws 147a, 147b respectively are preloaded helicaltorsion springs (not shown). The torsion springs apply a torque thatrotates torsion spring preloaded levers 136a, 136b toward contact ofslotted clamps 140a, 140b with the edge of wafer 160. Fixed slottedclamps 138a, 138b act as stops to prevent overrotation of torsion springpreloaded levers 136a, 136b, respectively.

In operation the edge of wafer 160 is held by slotted clamps 138a, 138b,140a, 140b under light spring tension, such that wafer 160 is positionedsubstantially concentric with the axis of annular ring 130. Slottedclamps 138a, 138b, 140a, 140b are disposed with their respective slotsin a plane parallel with but offset from annular ring 130, to provideaccess for cleaning and handling wafer 160, and are disposed about thecircumference of annular ring 130 in a configuration to prevent movementof wafer 160 relative to slotted clamps 138a, 138b, 140a, 140b and tofacilitate wafer loading and unloading. Slotted clamp parts are keptthin to minimize interference with wafer cleaning brushes 203a, 203b.The inner diameter of annular ring 130 is made large enough to provideadequate clearance for wafer cleaning brush 203a, 203b during thecleaning operation, The preload of preloaded levers 136a, 136b, is setat a value high enough to keep levers 136a, 136b from opening undercentrifugal force during rotation of ring assembly 128 and low enough toavoid wafer breakage from mechanical stress.

Ring assembly 128 rotates about the central axis of annular ring 130,supported by two grooved rolls 132a, 132b contacting an outercircumference and one grooved roll 132c contacting an innercircumference of annular ring 130. Grooved rolls 132a, 132b, 132c areoriented such that their respective grooves lie in the same verticalplane as that of annular ring 130. One grooved roll, e.g. grooved roll132a, is driven using a belt-and-pulley arrangement or otherconventional means; the remaining two grooved rolls, e.g. grooved rolls132b, 132c, rotate freely on their respective shafts. Particularly, theshaft of grooved roll 132c is mounted into an adjustably preloaded arm134, allowing control of contact pressure between annular ring 130 andthree grooved rolls 132a-132c. Using only one drive roll ensures slipfree rotation and therefore no particle generation. Preloaded arm 134carrying grooved roll 132c can be swiveled, thereby providing access toremove or exchange entire ring assembly 128. Interchangeability of ringassemblies supports multiple wafer size processing capability. Not onlyround wafers, but square, rectangular, etc. shaped substrates can beprocessed. Each ring assembly may be configured for a distinct substratesize and shape. Typically grooved rolls 132a, 132b may remain in theirrespective positions during interchange of ring assemblies.

FIG. 9b is a cutaway isometric view of wafer drive apparatus 126 asconfigured for wafer loading and unloading. For wafer loading orunloading, rotation of ring assembly 128 is first stopped in a homeorientation, i.e. with contact pins 146a, 146b in their lowest position.An air cylinder (not shown) extends a release bar 142 through a slot 144in the bottom panel 148 of wafer drive apparatus 126 disposedsubstantially parallel with the plane of annular ring 130. Release bar142 pushes against contact pins 146a, 146b, causing torsion springpreloaded levers 136a, 136b to pivot, thereby slidably withdrawingslotted clamps 140a, 140b from the edge of wafer 160. Slotted clamps140a, 140b and preloaded levers 136a, 136b are pivoted away from wafer160, allowing sufficient clearance to slide wafer 160 out of lower fixedslotted clamps 138a, 138b, thereby unloading wafer 160.

To load a wafer 160, the wafer edge is first inserted into lower fixedslotted clamps 138a, 138b. The air cylinder is depressurized, graduallywithdrawing release bar 142 and thereby releasing pressure from contactpins 146a, 146b. Preloaded levers 136a, 136b then return under springtension to their respective preset operating positions (see FIG. 9a)with upper slotted clamps 140a, 140b slidably engaging the circumferenceof wafer 160.

In accordance with the alternative embodiment, wafer drive apparatus 126provides true slip free rotation by using one driver roll only. Iteasily accommodates multiple wafer sizes including substrates withshapes other than round, facilitating flexible manufacturing. Itcomprises fewer rotating parts than other embodiments, leading to asimplified drive mechanism and less particle generation. It requires norelative motion between wafer and clamps during operation withpotentially reduced abrasion and risk of wafer breakage.

FIGS. 10a-10c are cutaway isometric views of various assemblies ofrinse/dry station module 106, in accordance with an embodiment of theinvention. Rinse/dry station module 106 employs the "MARANGONI" method,familiar in the art, wherein a dynamically changed surface tensionmechanism promotes drying a wafer without spinning. Generally a smallamount of isopropyl alcohol (IPA) is evaporated with nitrogen gas andapplied onto a wet wafer surface.

Combined rinse/dry station module 106 contains a stationary receiveframe 310 in which wafer 160 is held during the rinse and dry cycles.Receive frame 310 incorporates a minimum of three slotted arms312a-312c, which support wafer 160 in a stationary vertical position.Two containment chambers 314a, 314b are movably mounted, each facing anopposite surface of wafer 160. O-rings 342 and a gasket 344 sealcontainment chambers 314a, 314b against each other when closed, forminga sealed container.

For clarity containment chamber 314b is shown shaded in FIG. 10a. Atleast one containment chamber 314a, 314b has a recess 316 in an innersurface facing wafer 160, with a distance, typically of the order of 12millimeters or less and preferably on the order of 6 millimeterswall-to-wall between inner walls containment chambers 314a, 314b whenclosed, to accommodate wafer 160. Illustratively, common guide rails 318and a shared drive mechanism 320 (see FIG. 10c) translate containmentchambers 314a, 314b toward or away from each other (closed/open), inaccordance with direction arrows 330.

Referring to FIG. 10a, in an open position (chambers 314a, 314b mostdistant from each other) wafer 160 and inner walls of chambers 314a,314b including recess 316 are exposed to a DI (deionized) water rinsefrom one or more rinse nozzles 322 mounted adjacent containment chamber314a. Rinse nozzles 322 are supplied with DI water through a valve V5and a rinse nozzle assembly 328 which may be assembled from conventionaltubing and fittings. Not shown for clarity is a second rinse nozzleassembly mounted adjacent containment chamber 314b. Containment chamber314a is also connected to a source of DI water through a valve V4 and asupply tube 346 connected to an inlet port near the top of containmentchamber 314a. An outlet port at the bottom of containment chamber 314ais connected through a tube 332 and an outlet metering valve assembly V6to a drain. An IPA vapor source (see FIG. 10b) is connected through afitting 348 in fluid communication with a narrow slot 326 extendinghorizontally above the full width of recess 316. Rinse nozzle assembly328 is protected by a cover 350, shown shaded in FIG. 10a.

FIG. 10b is a cutaway isometric view of an IPA vapor source assembly334, which is connected by conventional tubing to containment chamber314a at fitting 348. IPA vapor source assembly 334 includes an IPAreservoir 324, which is connected via a refill tube 336 and a valve V2to a remote refill supply of liquid IPA. A submerged tube 338 with smallperforations (not shown) in IPA reservoir 324 is connected to a remotesource of nitrogen or other suitable carrier gas through gas tube 340and valve V1. Optional liquid level sensors are positioned in IPAreservoir 324. The outlet for IPA vapor from IPA reservoir 324 isconnected to the low pressure inlet port of an aspirator 352. The outletport of aspirator 352 is connected to containment chamber 314a (see FIG.10a) through outlet fitting 354 and conventional tubing. The highpressure inlet port of aspirator 352 is connected to valve V3, which maybe alternately toggled through a gas supply tube 356 to a remote sourceof nitrogen (not shown) or through an exhaust tube 358 to an exhaustport (not shown).

FIG. 10c is a cutaway isometric view of rinse/dry station module 106with containment chambers 314a, 314b in the closed position. Containmentchambers 314a, 314b are slidably attached to guide rails 318 and aretranslated into open and closed positions by shared drive mechanism 320as indicated by directional arrows 330. Rinse nozzles 322 connected torinse nozzle assembly 328 are located outside but adjacent tocontainment chambers 314a, 314b. An outlet port at the bottom ofcontainment chamber 314a is connected through a tube 332 and an outletmetering valve assembly V6 to a drain. Illustratively, rinse nozzleassembly 328 tube 332, and outlet metering valve assembly V6 are locateddifferently in FIG. 10a and FIG. 10c.

In operation containment chambers 314a, 314b are in the open position,while wafers 160 are being transported or in a standby status. Innersurfaces including recess 316 of containment chambers 314a, 314b arerinsed for a predetermined time by rinse nozzles 322 after which valveV5 is shut off and wafer 160 is placed in receive frame 310. Then valveV5 is turned on again to rinse wafer 160 and containment chambers 314a,314b, and after a predetermined time is again shut off. Alternativelyvalve V5 may remain open during wafer placement. The containmentchambers 314a, 314b move to the closed and sealed position. Valve V4 isthen turned on, allowing containment chambers 314a, 314b to fill with DIwater. Concurrently valve V1 is turned on, admitting nitrogen or othersuitable gas into IPA reservoir 324. The nitrogen bubbles released intothe liquid IPA promote evaporation of IPA and concurrently create apressurized atmosphere within IPA reservoir 324. After wafer 160 iscompletely submerged in DI water, valve V4 is shut off. Valve V3 is nowswitched from exhaust to nitrogen supply, producing a Venturi effect inaspirator 352 that pulls IPA vapor with carrier gas from IPA reservoir324 and delivers it through fittings 354 and 348 into slot 326 ofcontainment chamber 314a.

Outlet metering valve assembly V6 is now opened allowing the DI water todrain from containment chambers 314a, 314b at a controlled rate. The DIwater is displaced uniformly by IPA vapor delivered through slot 326,uniformly drying wafer 160. After the DI water has drained completelyand wafer 160 is dry, valve V3 is toggled to the exhaust position toprevent vapors from escaping from containment chambers 314a, 314b, whenthey return to the open position. Containment chambers 314a, 314b thenopen, and concurrently outlet metering valve assembly V6 closes. Drywafer 160 is removed from receive frame 310, and as soon as it hascleared rinse/dry station module 106, the cycle begins again withrinsing of inner surfaces of containment chambers 314a, 314b by rinsenozzles 322.

Advantageously, the present embodiment enables minimal single waferprocess time and minimal IPA and DI water consumption due to the smallvolume of containment chambers 314a, 314b. Inner surfaces of containmentchambers 314a, 314b are rinsed with DI water by rinse nozzles 322,starting as soon as dry wafer 160 is clear of rinse/dry station module106 and continuing simultaneously with loading of the next wafer 160 anduntil inner surfaces of containment chambers 314a, 314b are flushed freeof contaminants and particles before moving into close proximity withwafer 160. The rate of water level drop is controlled and varied bysetting the nitrogen gas pressure at the high pressure inlet port ofaspirator 352 and outlet metering valve V6. IPA vapor may be separatedfrom other drain discharge by valve V6 or via a recovery system ofconventional design beyond valve V6 (not shown).

Different size wafers may be accommodated by replacing the receiveframe. To reduce the volume between the two containment chambers for asmaller wafer, inserts or custom containment chambers may be used. Waterconsumption may then remain substantially proportional to wafer size.

An alternative embodiment allows only a single IPA reservoir to supplymultiple rinse/dry station modules 106. A valve between remote IPAreservoir and containment chambers 314a, 314b may control the amount ofIPA vapor dispensed. To minimize consumption, this valve is positionedas close as possible to containment chambers 314a, 314b, which are thenfilled with vapor only as needed.

In a further alternative approach, IPA vapor is generated by means of anatomizing nozzle mounted in single or multiple IPA reservoirs. The fluidport of the atomizing nozzle is connected to the IPA refill source, andthe atomizing gas port is connected to a source of nitrogen or othersuitable inert carrier gas. In accordance with this alternativeapproach, small droplets of IPA are sprayed into the IPA reservoir,where they evaporate and mix with nitrogen carrier gas. The IPA/nitrogenmixture then flows to containment chambers 314a, 314b in the samefashion as described in the previous approach.

Numerous wafer transport system designs are familiar in the art. Thewafer transport apparatus described herein is configured to the specificneeds of overall wafer cleaning and drying apparatus 100, in accordancewith the present invention.

FIG. 11a is a cutaway isometric view of wafer transport apparatus 108,in accordance with an embodiment of the invention. Wafer transportapparatus 108 moves wafers 160 between first brush station module 102,second brush station module 104, and rinse/dry station module 106,collectively hereinafter process modules 102, 104, 106. Wafer transportapparatus 108 transfers wafers 160 in sequence from one process module102, 104, 106 to the next (module locations are indicated by wafers onlyfor clarity).

Illustratively, wafer cleaning and drying apparatus 100 is configuredwith process modules 102, 104, 106 equally spaced in sequence ofoperation and aligned so that wafers 160 contained and fully engagedtherein have their respective surfaces in parallel planes and theirrespective centerlines along a common axis, hereinafter module axis 458.Additional transfer modules, hereinafter receive module 460 and sendmodule 462, are positioned and aligned at the beginning and end,respectively of the sequence of process modules 102, 104, 106. Receivemodule 460 receives wafer 160 from a previous operation and send module462 sends water 160 to a subsequent operation after the wafer cleaningand drying processes of wafer cleaning and drying apparatus 100.

A substantially cylindrical spacing bar 420 is rotationally mounted in atransport housing 422 with its longitudinal axis parallel to module axis458. Rotation of spacing bar 420 in transport housing 422 is actuated bya belt and pulley assembly (not shown) driven by a stepper motor 440attached to transport housing 422 or by other conventional means.

Illustratively, four lever assemblies 414a-414d are each attached by oneend radially to spacing bar 420 at equal rotational orientation and withsubstantially equal longitudinal spacing. Generally the number of leverassemblies 414a-414d attached to spacing bar 420 is one fewer than thetotal number of process and transfer modules. Lever assemblies 414a-414dare individually adjustable on spacing bar 420 both longitudinally androtationally, as detailed below. Paired end effectors 412 with fourattached grooved cylinders 410 are swivelably mounted onto a portion ofeach lever assembly 414a-414d distal to spacing bar 420.

FIGS. 12, 13 are cross-sectional views of wafer transport apparatus 108at a typical process module 102, 104, 106 during different stages of thewafer transport cycle. Referring to FIG. 12, wafers 160 are grippedvertically at their edges by four grooved cylinders 410. A wafer edge isgripped by the grooves so that wafer 160 is fixed in both radial andlongitudinal position relative to end effectors 412 during wafertransfer.

Consecutive grooved cylinders 410 are positioned on an end effector 412symmetrically relative to the centerline of wafer 160 such that thedistance between consecutive grooved cylinders 410 is greater than thelength of a flat on the wafer. Alternatively, if wafer 160 has one ormore flats or notches, or is of a different size, the configuration ofend effectors 412 and grooved cylinders 410 may be modified accordinglyto meet a specific requirement. Illustratively, for wafers 160 havingone or more flats or notches, grooved cylinders may be replaced byconventional elastically deformable edge gripping arms, as described forexample in Kudo et al. U.S. Pat. No. 5,547,515, provided that the lengthof a gripping surface is greater than the length of a notch or flat. Endeffectors 412 may be removed, replaced, and interchanged on leverassemblies 414a-414d using conventional means such as threadedfasteners.

Spacing bar 420 with attached lever assemblies 414a-414d is rotatable intransport housing 422 typically by 90 degrees, thereby causing distallymounted end effectors 412 with attached grooved cylinders 410 to pickand place wafers 160 at process modules 102, 104, 106. End effectors 412are mounted to lever assembly 414a-414d symmetrically relative to thecenterline of wafer 160 when rotated into a process chamber (not shownfor clarity). End effectors 412 have an open and a closed position. Inthe closed or "normal" position, shown in FIG. 12, end effectors 412clamp wafer 160 into grooved cylinders 410. In the open position, shownin FIG. 13, end effectors cause grooved cylinders 410 to release wafer160.

FIG. 11b is a cutaway isometric view of the detailed structure of leverassembly 414a-414d and spacing bar 420 as shown in FIG. 11a above. Leverassembly 414a-414d comprises an arm 372, a cover 374 (shown in brokenlines for clarity), and a mounting/alignment block (hereinafter block376), which interconnects lever assembly 414a-414d with spacing bar 420.The elements of the swivel mechanism for end effectors 412 mount ontoarm 372. Mounting holes, bores for bearing installation, and recessesfor actuators and supply tubing (not shown) are provided in arm 372.Cover 374 slides over arm 372 and attached mechanisms from the free endof arm 372 toward block 376, sealing and protecting the enclosedcomponents from fluids and debris. An O-ring 378 forms a seal betweenarm 372 and cover 374. Lateral openings are provided in the cover forthe swivel shafts of end-effectors 412. Labyrinth type seal assemblies(not shown) are installed around the swivel shafts of end-effectors 412between the outside of cover 374 and end effectors 412 to secure cover374 in place, to prevent outside fluids from entering lever assembly414a-414d, and to prevent possible contaminants within lever assembly414a-414d from emerging.

Block 376 interconnects lever assembly 414a-414d to two mounting bars380, which are internal to and extend parallel to one anothersubstantially the full length of spacing bar 420. Block 376 containsclearance slots 402 that slide over mounting bars 380 and a flat section382 that fits between mounting bars 380. Bar mounting screws 386 secureblock 376 through oversize clearance holes to mounting bars 380. Aflange section 384 of block 376 is secured to arm 372 through oversizecurved clearance slots in flange section 384 by arm mounting screws 388.Set screws 390 engaging flange section 384 bear against the flat surfaceof arm 372 in opposition to arm mounting screws 388, to adjust thelongitudinal and angular alignment between block 376 and arm 372. Setscrews 390 cooperatively with oversize mounting holes and slots allowadjustment of lever assemblies 414a-414d individually with respect tothe longitudinal axis of spacing bar 420 in all six translational androtational degrees of freedom. Thus block 376 serves as a universaladjustment structure for aligning lever assembly 414a-414d with processmodules 102, 104, 106.

To protect mounting bars 380, block 376, supply lines 392 as well asother utilities and mechanisms (not shown), a retractable cover 394 isinstalled around spacing bar 420. Retractable cover 394 comprises twocover cups 396 connected by a flexible bellows 398. The faces of covercups 396 have O-ring grooves 400 with O-rings (not shown) to sealagainst the flat surface of arm 372. Bellows 398 contracts to allowaccess to block 376 and flexes to accommodate alignment settings oflever assembly 414a-414d. The ends of spacing bar 420 are sealed withcaps 404 attached to the outside flat surfaces of arms 372 of end leverassemblies 414a, 414d.

The swivel mechanism for end effectors 412 is actuated by a pneumaticcylinder 472. Preferred is a conventional single-acting, spring extendedcylinder. The cylinder rod is attached to a belt clamping block 474,which holds one end of a double sided open-ended timing belt(hereinafter timing belt 476). The other end of timing belt 476 isattached to a coil spring 478 to maintain tension. The spring load andthe mounting position of extended pneumatic cylinder 472 define theamount of preload transmitted to end effectors 412 in their closedposition. Timing belt 476 is threaded around two pulleys 480 connectedto the swivel shafts of end effectors 412, which translate the linearmotion of timing belt 476 into swivel motion of the end effectors 412.Position sensors 482, preferably employing inductive means, verify theactual end effector orientations by detecting the positions of pins 484installed in pulleys 480.

The end effector orientation having the lowest spring tension is theclosed orientation shown in FIG. 11b. In operation, when pneumaticcylinder 472 is pressurized, timing belt 476 is pulled toward pneumaticcylinder 472, and end effectors 412 swivel open. A lock lever 486 ispreloaded against belt clamping block 474 by a torsion spring (notshown). When belt clamping block 474 reaches the limit of its traveltoward pneumatic cylinder 472, it releases lock lever 486, which snapsupward, blocking the return path of belt clamping block 474. Endeffectors 412 are now in the open orientation and are prevented fromclosing unless lock lever 486 is removed. In normal operation a pincylinder 488 attached to a mounting block 490 and pressurized through apneumatic supply line 492 pushes against lock lever 486, causing locklever 486 to rotate clear of belt clamping block 474. Pneumatic cylinder472 is then depressurized through a flow control valve (not shown),allowing smooth and gradual closing of end effectors 412.

If a power failure, pressure loss, or emergency shutdown occurs when endeffectors 412 are in the open orientation, then lock lever 486 ensuresthat they remain in the open orientation and out of contact with wafers160. If such a loss occurs when end effectors 412 are closed or inmotion, however, end effectors 412 smoothly and gradually close as innormal operation.

A rinse nozzle 416 mounts on the end of cover 374 distal from spacingbar 420 and is fed by a fluid supply tube 494 running through themounting end of arm 372 and through spacing bar 420.

Rinse nozzles 416 mounted for example as shown in FIG. 11b to leverassemblies 414a-414c keep wafers 160 moist during the transport cycleuntil wafers 160 have been dried, as is typically required during postCMP (chemical-mechanical-polishing) wafer processing applications. Leverassembly 414d does not require a rinse nozzle, because its travel isbetween rinse/dry station module 106 and send module 462, after thesurfaces of wafer 160 have been dried.

Referring to FIGS. 11a, 12, 13, transport housing 422 translateslongitudinally along the center axis of spacing bar 420, parallel tomodule axis 458. Transport housing 422 is supported by a ball bushingassembly 446 that slides on a linear rail 424 and is driven typically bya linear motor 426. Linear rail 424 and linear motor 426 are attached toa frame assembly 442. Spacing bar 420 houses tubing and cabling routedfrom a utility harness 444 to individual lever assemblies 414a-414d andtheir respective mechanisms.

A cover 428 located below transport housing 422 collects fluids fromrinse nozzles 416 and process modules 102, 104, 106 and discharges theminto a waste double containment reservoir 430, in accordance withconventional practice. Cover 428 contains a slot (not shown) underlyingtransport housing 422, through which transport housing 422 mechanicallycommunicates with ball bushing assembly 446. The slot is surrounded by avertical lip (not shown), which together with the underside of transporthousing 422 forms a baffle that prevents process fluids from enteringthe slot, thereby protecting linear rail 424 and linear motor 426 fromexposure to and potential damage from chemicals and fluids.

FIGS. 14a-14h illustrate a typical operating sequence for a transportcycle of wafer transport apparatus 108.

FIG. 14a is an isometric view of water transport apparatus 108 in oneend position at the beginning of a transport cycle (home position) inaccordance with the present embodiment. Wafers 160 are contained inprocess modules 102, 104, 106 and in receive module 460. Leverassemblies 414a-414d are oriented vertically.

FIG. 14b is an isometric view of wafer transport apparatus 108 at afurther stage of a transport cycle, in accordance with the presentembodiment. Spacing bar 420 rotates lever assemblies 414a-414d by 90degrees into a horizontal orientation, thereby rotating end effectors412 into modules 460, 102, 104, 106 without interference and swivelingend effectors 412 into the open position to receive wafers 160.

FIG. 14c is an isometric view of wafer transport apparatus 108 at afurther stage of the transport cycle, in accordance with the presentembodiment. After lever assemblies 414a-414d are in a horizontalorientation, end effectors 412 swivel into the closed position, clampingwafers 160 on their edges into grooved cylinders 410. Rinse nozzles 416aim at wafers 160 and dispense fluids (typically deionized water).

FIG. 14d is an isometric view of wafer transport apparatus 108 at afurther stage of the transport cycle, in accordance with the presentembodiment. Spacing bar 420 rotates lever assemblies 414a-414d back intoa vertical orientation, carrying wafers 160 clear of modules 460, 102,104, 106 (not shown). The relative position between wafers 160 and rinsenozzles 416 remains constant throughout the travel.

FIG. 14e is an isometric view of wafer transport apparatus 108 at afurther stage of the transport cycle, in accordance with the presentembodiment. Spacing bar 420 translates longitudinally by the width ofone module 460, 102, 104, 106 (not shown), advancing all four wafers 160simultaneously by one module width, to positions adjacent theirrespective next modules. For example, the wafer previously in receivemodule 460 is moved adjacent first brush station module 102, the waferpreviously in first brush station module 102 is moved adjacent secondbrush station module 104 the wafer previously in second brush stationmodule 104 is moved adjacent rinse/dry module 106, and the waferpreviously in rinse/dry module 106 is moved adjacent send module 462(not shown), respectively. Rinse nozzles 416 maintain a constantposition in relation to wafers 160.

FIG. 14f is an isometric view of wafer transport apparatus 108 at afurther stage of the transport cycle, in accordance with the presentembodiment. Spacing bar 420 again rotates lever assemblies 414a-414dinto a horizontal orientation, thereby carrying wafers 160 into nextmodules 102, 104, 106, 462, respectively.

FIG. 14g is an isometric view of wafer transport apparatus 108 at afurther stage of the transport cycle, in accordance with the presentembodiment. After wafers 160 are securely engaged by the respectiveholding devices of next modules 102, 104, 106, 462, end effectors 412swivel into the open position, thereby releasing wafers 160 from groovedcylinders 410. Rinse nozzles 416 may then be turned off.

FIG. 14h is an isometric view of wafer transport apparatus 108 at afurther stage of the transport cycle, in accordance with the presentembodiment. Spacing bar 420 rotates lever assemblies 414a-414d againinto a vertical orientation. The next wafer cleaning and drying cyclecan then start. Spacing bar 420 carrying lever assemblies 414a-414dtranslates back to the home position, as shown in FIG. 14a, to await thenext transport cycle. The return to the home position may be performedsimultaneously with all or part of the ongoing wafer cleaning and dryingcycle, thereby reducing cycle time and increasing throughput.

At the beginning of a production cycle, only receive module 460 containsa wafer. In the first transport cycle, wafer transport apparatus 108captures and transfers the single wafer from receive module 460 to firstprocess module 102, 104, 106 as described above in connection with FIGS.14a-14h. In the second transport cycle, wafer transport apparatus 108captures and transfers the first wafer from first process module 102,104, 106 to second process module 102, 104, 106 and simultaneouslycaptures and transfers a second wafer from receive module 460 to firstprocess module 102, 104, 106. In each successive transport cycle thewafer transport apparatus 108 transfers one additional wafer to oneadditional module, until each module 460, 102, 104, 106, 462 contains awafer. At the end of a production cycle wafer transport apparatus 108transfers one fewer wafer in each successive transport cycle, until onlysend module 462 contains a wafer.

Wafer transport apparatus 108, in accordance with the embodiment,provides efficiency by transferring multiple wafers simultaneously amongmultiple process modules 102, 104, 106. It occupies a minimal footprintwithout interference with process modules 102, 104, 106. It provides fora continuous wafer rinse capability with constant relative positionbetween wafer and rinse nozzle throughout the transport cycle. Return ofspacing bar 420 with attached lever assemblies 414a-414d to its homeposition during an ongoing cleaning and drying cycle reduces wafertransport overhead and increases throughput. End effectors can easily beinterchanged for flexibility to accommodate different wafer sizes andshapes.

In an alternative version of the embodiment, end effectors 412 may bereplaced partially or altogether by conventional vacuum end effectorassemblies (e.g. holding the wafer surface under air pressure), withoutsubstantially changing the function or the structure of wafer transportapparatus 108. However, as is known in the art, this method has inferiorreliability for handling wet and slippery wafers.

In a further alternative version of the embodiment, linear motor 426 maybe replaced by a pneumatic cylinder. Likewise stepper motor 440 may bereplaced by a rotary pneumatic cylinder, resulting potentially in anentirely pneumatically driven wafer transport apparatus 108. It isunderstood that all cleaning, rinsing, drying, and transport functionsof wafer cleaning and drying apparatus 100 are preferably controlled bysoftware, although alternative methods may be used in whole or in part.

Although a system is described, it is to be understood that theembodiments comprise each module thereof individually. Having thusdescribed the principles of the invention, together with severalillustrative embodiments thereof, it is to be understood that, althoughspecific terms are employed, they are used in a generic and descriptivesense, and not for the purpose of limitation, the scope of the inventionbeing set forth in the following claims.

What is claimed is:
 1. A method for cleaning and drying a semiconductorwafer having a first planar surface and a second planar surface oppositesaid first planar surface and having a midplane parallel to andequidistant between said first and second planar surfaces, comprisingthe steps of:placing a wafer in a wafer drive assembly; rotating saidwafer about a rotation axis in said wafer drive assembly with saidplanar surfaces of said wafer oriented in a vertical plane and with saidrotation axis aligned perpendicular to said planar surfaces; cleaningsaid wafer with first and second wafer cleaning brushes disposedsymmetrically with respect to said midplane of said wafer, said firstand second wafer cleaning brushes comprising, respectively, first andsecond substantially tubular sponges rotatable beltwise about respectivebrush axes parallel to said planar surfaces, said first wafer cleaningbrush comprising a first brush shaft and a second brush shaft, saidfirst and second brush shafts being rotatable about mutually parallelaxes and spaced laterally from each other, said first and second brushshafts being mounted within a lumen of said first substantially tubularsponge; rotating said first sponge in a first direction while said firstsponge is in contact with said first planar surface of said wafer, androtating said second sponge in a second direction opposite said firstdirection while said second sponge is in contact with said second planarsurface of said wafer, said cleaning step being performed concurrentlywith said rotating step; and removing said wafer from said wafer driveassembly.
 2. The method according to claim 1, wherein said first andsecond brush shafts are spaced laterally from each other by anadjustable distance.
 3. The method according to claim 2, wherein saidfirst wafer cleaning brush further comprises at least one fluid deliverytube mounted within said lumen of said first sponge, said fluid deliverytube being nonrotating and aligned parallel with said first and secondbrush shafts and containing perforations for dispensing fluid uniformlyalong substantially the lengths of said brush shafts.
 4. The methodaccording to claim 3, wherein the step of cleaning further comprisesdispensing fluid from said fluid delivery tube concurrent with therotation of said first sponge of said first wafer cleaning brush, suchthat said fluid irrigates a portion of an inner surface of said firstsponge directly after said portion passes around said first brush shaft.5. The method according to claim 3, wherein the step of cleaning furthercomprises dispensing fluid from said fluid delivery tube concurrent withthe rotation of said first sponge of said first wafer cleaning brush,such that said fluid irrigates a portion of an inner surface of saidfirst sponge directly after said portion passes around said second brushshaft.
 6. The method according to claim 2, wherein the steps of placingand removing a wafer further comprise swiveling said first wafercleaning brush about an axis concentric with said first brush shaftclear of said wafer drive assembly before placing said wafer.
 7. Themethod according to claim 1, wherein the steps of placing a wafer andremoving a wafer further comprise transferring said wafer in a wafertransport assembly configured to transfer at least two waferssimultaneously, comprising the steps of:rotating a substantiallycylindrical member having a longitudinal axis and being mounted in ahousing from a home position by substantially ninety degrees in a firstrotational direction about said longitudinal axis, said housing beingtranslatable parallel to said longitudinal axis, said substantiallycylindrical member being attached to at least two substantially parallelmembers disposed radially relative to said substantially cylindricalmember, said at least two substantially parallel members eachinterconnected radially to said substantially cylindrical member througha mounting/alignment block, said mounting/alignment block enablingalignment between each of said at least two substantially parallelmembers and said substantially cylindrical member, an end effector beingswivelably connected to each of said at least two substantially parallelmembers; swiveling said end effector in a first swivel directionrelative to each of said at least two substantially parallel members,thereby receiving said wafer; swiveling said end effector in a secondswivel direction opposite said first swivel direction, thereby capturingand holding an edge of said wafer in a precise position and orientationrelative to said at least two substantially parallel members; rotatingsaid substantially cylindrical member by substantially ninety degrees ina second rotational direction opposite said first rotational direction,thereby removing said wafer; translating said housing by a predetermineddistance in a first longitudinal direction; rotating said substantiallycylindrical member by substantially ninety degrees in said firstrotational direction; swiveling said end effector in said first swiveldirection, thereby releasing said wafer; rotating said substantiallycylindrical member by substantially ninety degrees in said secondrotational direction; and translating said housing by said predetermineddistance in a second longitudinal direction opposite said firstlongitudinal direction, thereby returning said housing to said homeposition, said translation in said second longitudinal directionoccurring concurrently with said steps of rotating and cleaning saidwafer.
 8. The method according to claim 7, further comprising directinga fluid spray from a fluid dispensing nozzle onto said wafersubstantially, continuously during said transfer of said wafer by saidwafer transport assembly, said fluid dispensing nozzle being attached toat least one of said at least two substantially parallel members in asubstantially constant position and orientation relative to said wafer.9. The method according to claim 7, wherein said mounting/alignmentblock enables alignment between each of said at least two substantiallyparallel members and said substantially cylindrical member in threetranslational and three rotational degrees of freedom.
 10. The methodaccording to claim 1, further comprising the steps of:placing said waferinto an open rinse/dry enclosure having an inner surface; directing afluid spray from at least one fluid dispensing nozzle adjacent saidenclosure onto said wafer and said inner surface of said enclosure;closing and sealing said rinse/dry enclosure to enclose said wafer, suchthat said wafer is stationary and all points on said planar surfaces ofsaid wafer are located at a distance no greater than six millimetersfrom said inner surface; immersing said wafer in a fluid within saidrinse/dry enclosure; draining said fluid through an outlet valve; dryingsaid wafer by exposing the surfaces of said wafer to a chemical vaporwithin said rinse/dry enclosure; opening said rinse/dry enclosure,thereby providing access to a dry wafer; and removing said dry waferfrom said rinse dry enclosure.
 11. The method according to claim 10,wherein the steps of placing a wafer and removing a wafer furthercomprise transferring said wafer in a wafer transport assemblyconfigured to transfer at least two wafers simultaneously, comprisingthe steps of:rotating a substantially cylindrical member having alongitudinal axis and being mounted in a housing from a home position bysubstantially ninety degrees in a first rotational direction about saidlongitudinal axis, said housing being translatable parallel to saidlongitudinal axis, said substantially cylindrical member being attachedto at least two substantially parallel members disposed radiallyrelative to said substantially cylindrical member, said at least twosubstantially parallel members each interconnected radially to saidsubstantially cylindrical member through a mounting/alignment block,said mounting/alignment block enabling alignment between each of said atleast two substantially parallel members and said substantiallycylindrical member, an end effector being swivelably connected to eachof said at least two substantially parallel members; swiveling said endeffector in a first swivel direction relative to each of said at leasttwo substantially parallel members, thereby receiving said wafer;swiveling said end effector in a second swivel direction opposite saidfirst swivel direction, thereby capturing and holding an edge of saidwafer in a precise position and orientation relative to said at leasttwo substantially parallel members; rotating said substantiallycylindrical member by substantially ninety degrees in a secondrotational direction opposite said first rotational direction, therebyremoving said wafer; translating said housing by a predetermineddistance in a first longitudinal direction; rotating said substantiallycylindrical member by substantially ninety degrees in said firstrotational direction; swiveling said end effector in said first swiveldirection, thereby releasing said wafer; rotating said substantiallycylindrical member by substantially ninety degrees in said secondrotational direction; and translating said housing by said predetermineddistance in a second longitudinal direction opposite said firstlongitudinal direction, thereby returning said housing to said homeposition, said translation in said second longitudinal directionoccurring concurrently with said steps of rotating and cleaning saidwafer.
 12. The method according to claim 11, further comprisingdirecting a fluid spray from a fluid dispensing nozzle onto said wafersubstantially continuously during said transfer of said wafer by saidwafer transport assembly, said fluid dispensing nozzle being attached toat least one of said at least two substantially parallel members in asubstantially constant position and orientation relative to said wafer.13. The method according to claim 11, wherein said mounting/alignmentblock enables alignment between each of said at least two substantiallyparallel members and said substantially cylindrical member in threetranslational and three rotational degrees of freedom.
 14. The methodaccording to claim 1, wherein the step of rotating is performed using awafer drive assembly comprising a rotatable ring assembly incorporatingan annular ring and means for clamping said wafer in a plane offset fromand parallel to the plane of said ring assembly.
 15. The methodaccording to claim 14, wherein said means for clamping comprises:apreloaded torsion spring lever swivelably attached to said annular ring;a slidable clamp attached to said preloaded torsion spring leveradjacent a first end of said preloaded torsion spring lever, saidslidable clamp gripping an edge of said wafer throughout the step ofrotating; a contact pin attached to said preloaded torsion spring leveradjacent a second end of said preloaded torsion spring lever oppositesaid first end; and an actuator that applies pressure radially to saidcontact pin, causing said preloaded torsion spring lever to swivel onsaid annular ring, thereby withdrawing said slidable clamp from saidwafer, said preloaded torsion spring lever returning under springtension to engage said wafer with said slidable clamp, when saidactuator ceases to apply pressure to said contact pin.